Types of CV Joints

Types of CV Joints

CV joints come in a variety of styles. The different types of joints can be referred to by position (inboard or outboard), by function (fixed or plunge), or by design (ball-type or tripod).

Inboard and Outboard Joints

In front-wheel-drive drivetrains, two CV joints are used on each half shaft. The joint nearer the transaxle is the inner of inboard joint, and the one nearer the wheel is the outer or outboard joint. In a rear-wheel-drive vehicle with independent rear suspension (IRS), the joint nearer the differential can also be referred to as the inboard joint. The one closer to the wheel is the outboard joint.

Fixed and Plunge Joints

CV joints either are fixed (meaning they do not plunge in and out to compensate for changes in length) or are a plunge joint (one that is capable of in-and-out movement).

In FWD applications, the inboard joint is also a plunge joint. The outboard joint is a fixed joint. Both joints do not need to plunge if one can handle the job. Further, the outdoor joint must also be able to handle much greater operating angles needed for steering.

In RWD applications with IRS, one joint on each axle shaft can be fixed and the other a plunge, or both can be plunge joints. Since the wheels are not used for steering, the operating angles are not as great. Therefore, plunge joints can be used at either or both ends of the axle shafts.

Ball-Type Joints

There are two basic varieties of CV joints: the ball-type and tripod-type joints. Both types are used as either inboard or outboard joints, and both are available in fixed or plunge designs.

Fixed Ball-Type Joints

The fixed ball-type, or Rzeppa joint, consists of an inner ball race, six balls, a cage to position the balls, and an outer housing. Tracks machined in the inner race and outer housing allow the joint to flex. The inner race and outer housing form a ball-and-socket arrangement. The six balls serve both as bearings between the races and the means of transferring torque from one to the other.

If viewed from the side, the balls within the joint always bisect the angle formed by the shafts on either side of the joint regardless of the operating angle. This reduces the effective operating angle of the joint by half and virtually eliminates all vibration problems. The input speed to the joint is always equal to the output velocity of the joint - thus the description "constant velocity." The cage helps to maintain this alignment by holding the six balls snugly in its windows. If the cage windows become worn or deformed over time, the resulting play between ball and window typically results in a clicking noise when turning. It is important to note that opposing balls in a Rzeppa CV joint always work together as a pair. Heavy wear in the tracks of one ball almost always results in identical wear in the tracks of the opposing ball.

Another ball-type joint is the dish style, which is used predominantly on Volkswagen as well as on many German rear-wheel-drive models. Its design is very similar to the Rzeppa joint.

Plunging Ball-Type Joints

There are two basic styles of plunging ball-type joints: the double-offset that uses a cylindrical outer housing with straight grooves, and the cross groove joint. This is a compact design with a flat, doughnut-shaped outer housing and angled grooves.

The double-offset joint is typically is typically used in applications that require higher operating angles (up to 25 degrees) and greater plunge depth (up to 2.4 inches). This type of joint can be found at the inboard position on some front-wheel-drive half-shafts, as well as on the propeller shaft of some four-wheel-drive shafts. The components of a double offset joint are typically held together as an assembly by a retaining ring.

The cross groove joint has a much flatter design than any other plunge joint. It is used as the inboard joint on FWD half-shafts or at either end of RWD independent rear suspension axle shafts. The feature that makes this joint unique is its ability to handle a fair amount of plunge (up to 1.8 inches) in a relatively short distance. The inner and outer races share the plunging motion equally, so less overall depth is needed for a given amount of plunge. The cross groove can handle operating angles up to 22 degrees.

Tripod CV Joints

As with ball-type CV joints, tripod joints come in two varieties: plunge and fixed.

Tripod Plunging Joints

Tripod plunging joints consists of a central drive part or tripod (also know as spider). This has three trunnion fitted with spherical rollers on needle bearings and an outer housing (sometimes called a tulip because if its three-lobed, flower-like appearance). On some tripod joints, the outer housing is closed, meaning the roller tracks are totally enclosed within it. On others, the tulip is open and the roller tracks are machined out of the housing. Tripod joints are most commonly used as FWD inboard plunge joints.

Fixed Tripod Joints

The fixed tripod joint is sometimes used as the outboard joint in FWD applications. In this design, the trunnion is mounted in the outer housing, and the three roller bearings turn against an open tulip on the input shaft. A steel locking spider holds the joint together.

The fixed tripod joint has a much greater angular capability. The only major difference from a service standpoint is that the fixed tripod joint cannot be removed from the half-shaft or disassembled because of the way it is manufactured. The complete joint and shaft assembly must be replaced if the joint goes bad.

More Drive Axles And Differentials

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